Metal Finishing Guide Book


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Assume motor efficiencies of 90% and 92%, a cost difference of $300, between the two motors. The cost of operating the 90% efficient motor: The cost of operating a 92% efficient motor: Annual savings for using a higher efficiency motor: $7,261 - $7,103 = $157/year Pay back for the higher efficiency motor: $300/$157 = 1.91 years After 1.91 years the high-efficiency motor has paid for its self. Savings incurred after 1.91 years and until the motor is replaced could be consider profit. GAS Heaters and ovens consume gas in a finishing system. Determining total gas consumption for an oven or heater is complicated and beyond the scope of this paper. The cost associated with the temperature adjustments of an oven, up or down, can be easily calculated. The temperature at which an oven operates de- termines the amount of gas consumed by the oven. Many factors effect the temperature settings, type of parts being cured, bake time, air flow, product, etc. Calculating the cost change when the temperature of the oven is changed can be accomplished using the following formula: SCFM is standard cubic feet per minute and can be attained from drawings for the oven or the blower supplier. The factor 1.1 is used to convert SCFM and ��F of air to BTU/hour. Example of how to use this formula is illustrated below. Oven Temperature Reduction The temperature of an oven was lowered 10��F due to an air duct modification. What are the cost savings? The SCFM is 30,000, the cost/MBTU is $4.00, the oven operates 20 hours a day, and the plant operates 245 days a year. Reducing the air temperature of the oven saved $6,468 dollars a year for this example. Gas savings are not the only savings that occur when the oven temperatures are reduced. 875

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